DHCP not assigning option 15 to L2TP VPN remote users

Balance 380 running firmware 6.3.4 (latest).

I’ve setup a DHCP scope on the router and specified option 15 (DNS Domain Name) with “ourdomain.local”. Remote users attaching via L2TP/RADIUS correctly receive an IP address in the DHCP range (as well as the correct DNS and Router “DHCP option 3” settings), but the DNS Domain Name does NOT get applied to the VPN connection. I’ve confirmed this with Windows 7, 8.1, and 10 remote PCs.

This results in the remote users being able to access shared LAN resources only via IP address or FULLY-qualified server name (ex: SERVER.ourdomain.local). Any attempts to access shared LAN resources by non-qualified name (ex: SERVER) fails. This results in previously-mapped drives, previously-saved UNC paths, previously-saved LAN URLs, etc. on the remote users’ PCs failing to resolve.

For the users who take their domain-connected notebook PCs out of the office to remotely connect via the VPN, the VPN is essentially useless when they can’t attach to mapped drives, etc.

Any ideas on how to correct this?